Electrical connector plug



Jan. 19, 1960 w. ELFENBEIN 2, 22,134

ELECTRICAL CONNECTOR PLUG F iled Jan. 5, 1956 BY y kdmd 2,922,134- Fatented Jan. 19, 196% United States Patent Qfiice ELECTRICAL CONNECTOR PLUG Wilfred Elfenbeim Dayton, Ohio Application January 5, 1956, Serial No. 557,587

Claims. (Cl. 339-14) This invention relates to electrical connector plugs, and more particularly to improved three-wire, grounding type connector plugs.

There has been a constant search for improvements in electrical equipment to afford added safety features thereto. One of the safety requirements that has been efiected in the national electric code is that exposed non-current carrying metal parts of portable electric equipment shall be grounded by means of a conductor included with the circuit conductors in the flexible power cord provided .therewith. This necessitates a suitable connector plug for the power cord including a grounding blade to be used with a suitable receptacle providing a ground return at the service entrance. To date, most grounding type connector plugs have been fabricated so as to provide them with rigidly connected ground blades. Plug designs employing displaceable ground blades have been proposed but they have had various unsatisfactory aspects which have prevented their acceptance. Accordingly, since to all practical purposes, grounding type connector plugs are generally only available with rigidly connected ground blades, adapters are required to enable their use in conventionalv two-pole utility outlets. Thus, the users of portable equipment are forced to go to the expense of purchasing adapters and the annoyance of stocking them at all times so they are immediately available.

The subject invention provides a simple solution to the above indicated problem. It provides an improved grounding type connector plug wherein the ground blade is connected thereto for simple and easy pivotal or axial displacement thereof for use of the plug with a conventional outlet of a two-pole nature where necessary. The invention contemplates, in its preferred form, that the displacement of the ground blade be automatic on application of the improved plug to a conventional two-pole utility outlet, and on removal of the plug that the ground blade automatically return to its operative position. This improved plug eliminates the need for adapters and requires no unnecessary handling or removal of plug components when an occasion requires its use in application to the conventional two-pole utility outlet.

An object of the invention is to provide a new and improved electrical connector plug.

A further object of the invention is to provide an improved three-wire, grounding type connector plug having a readily adjusting ground blade adapting it for selective use with a conventional two-pole utility outlet without the necessity for removal or mutilation of the ground blade.

Another object of the invention is to provide a new and improved three-wire, grounding type electrical connector plug including a ground blade so connected therewith to automatically adapt itself for selective application to a conventional two-pole utility outlet or to a service receptacle accommodating the ground blade.

An additional object of the invention is to provide an 7 improved three-wire grounding type electrical connector plug havingfthe advantageous structural features, the

inherent meritorious characteristics, and the mode of operation herein mentioned.

With the above primary and other incidental objects in view, as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation, or their equivalents as hereinafter described or illustrated in the accompanying drawings.

In the drawings wherein is shown the preferred, but obviously not necessarily the only forms of embodiment of the invention,

Fig. 1 is an end view of a three-wire, grounding type electrical connector plug providing a preferred embodiment of the invention.

Fig. 2 is a side View of the plug shown in Fig. 1.

Fig. 3 is a schematic view of the plug of Fig. 1 as applied to a conventional two-pole utility outlet.

Fig. 4 is a perspective view of a plug providing a further embodiment of the invention.

Fig. 5 is a fragmentary view of the plug as shown in Fig. 4 indicating the disposition of the ground blade thereof when the plug is applied to a conventional two-pole utility outlet.

Fig. 6 presents a perspective view of another modification afforded by the invention.

Fig. 7 is a fragmentary view of the plug as shown in Fig. 6 with the ground blade thereof in its inoperative position.

Fig. 8 is a perspective view of an additional embodiment of the invention.

The invention can best be described with reference to the embodiments thereof presented in the drawings. Noting Figs. 1-3 of the drawings, a preferred embodiment is shown therein. It consists of a circular plug body 1 of Bakelite or other suitable insulating material having a central aperture 2 therein for passage of a power cord therethrough. A metal casing 3 is provided about the sides of body 1 and to therear thereof wherein a central aperture is provided to coincide with the aperture 2 in the body 1. A split cable or cord clamp 4 is provided to the rear of the body 1 having angled base projections thereof seating between the rear surface of the body 1 and the casing 3 and clamped therebetween. Screws 5 connect the sections of the cord clamp for relative adjustment thereof to accommodate and fix a power cord relative the plug body.

The end face of the plug body is recessed at 6 and 7 to respectively seat base plates 8 and 9 of circuit contact blades 10 and 11 thereto. Screws 12 engage the base plates and 9 to the plug body. Terminal screws 13 are also engaged in each of the base plates 8 and 9 for respective engagement of the circuit conductors of the associated power cord thereto. The circuit contact blades 10 and 11 are integrally connected to their respective base plates so as to project at right angles to the face of the plug body 1.

A third recess 14 is provided to one side of the end face of the plug body. A base plate 15 is seated therein and connected thereto by a screw 16. Integrally connected to the base plate 15 and extending vertically therefrom is a U-shaped bracket 17 having the legs thereof extending outwardly of the end face of the plug body. A pivot pin 18 connects the parallel legs of the bracket 17 and is fixed thereto. A ground blade 19, which is U- shaped in horizontal cross-section and longer than the circuit blades 16 and 11, is pivotally mounted to the pin 18 adjacent the inner end thereof. The ground blade 19 is so disposed that the open side thereof faces outwardly to the side of the body 1. A coil spring 20 is wrapped about the pin 18 and has one extremity anchored to engage the base plate 15 and the other extremity seating to the end face of the plug body 1. The outer end of the ground blade 19 has a slope 21 therein for purposes to be described. The side of the plug body 1 and the casing 2, adjacent the recess 14 in thepath of the ground blade, is notched at 22 to accommodate a 90 pivoting of the blade from its normal projected position as eflfectedby the bias of the spring 20. A terminal screw 24 is connected to the base plate 15 for connection of the ground conductor of a three Wire power cord thereto.

An improved three-wire, grounding type electrical connector plug is thus provided. The respective base plates 8, 9, and 15 in the plug afliord terminal connection of the circuit and ground conductors of a power cord of a piece of portable electrical equipment. In the event a proper three-pole grounding receptacle is provided for connection of the plug to power the equipment associated therewith, as the plug is applied, the ground blade being longer first engages in its appropriate socket and then the circuit blades seat to afford a power and ground connection for the electrical equipment thereby.

of the receptacle R causing it to be cammed outwardly of the plug body to extend at right'angles to its normal projected position through notch 22 in the side of the plug body 1 and casing 2. This is effected as the circuit contact blades 10 and 11 of the plug seat in the two-pole utility outlet and it is automatic in nature. The pivoting of the blade 19, of course, is against the bias of the spring so that as the plug is removed from the receptacle the ground blade will be immediately and automatically returned to its normal projected position by the spring 20. Thus, the plug requires no manual adjustment of any sort to adapt it for selective use with a two-pole receptacle or a three-pole receptacle which affords a ground return for grounding of the non-current carrying metal parts of the electrical equipment Withwhich the plug is employed. a

Figs. 4 and 5 of the drawings present a further'e'mbodiment of the invention. In the form of the plug provided herein conventional circuit contact blade are provided as indicated previously. As shown, a ground blade 49 is pivotally connected by a pin 41 to the side of the plug body and the casing therefor. The base of the blade 40 is circular in nature and provided with a peripheral notch 42 which is axially aligned with the projecting end of the ground blade. An additional peripheral notch.43

4. biased relation in the notch 42 in the base of the blade to maintain the projected position thereof.

Figs. 6 and 7 present another modification of the plug of Fig. 1 of the drawings. In this instance the metal casing 2" of the plug at one side thereof is provided with a longitudinal groove 5! A pin 51 is fixed in the side of the casing centrally within the groove 50. The outer end of the pin 51 has a cap 52 fixed thereto. A ground blade 53 is pivotally' mounted adjacent the inner end thereof on the pin 51. A coil, spring 54 about the pin 51 and engaged at its respective ends to cap 52 and the ground blade 53 normally biases theground blade 53 into engagement with the plug casing in the groove 50, causing the blade thereby to normally project vertically relative the end face of the plug as do the conventional circuit contact blades thereof. This affords a normal ground connector to the plug where an appropriate receptacle is available. To utilize the plug with a conventional twopole utility outlet, the ground blade 53 is moved outwardly on the pin 51 against the bias of spring 54 and rotated 90 in which position the bias of the spring will position.

Fig. 8 of the drawings presents another preferred embodiment of the invention. The plug is conventional as to the circuit blades provided therein but the ground blade is pivotally connected by pin 61 to one side of the plug body. The inner pivoted end of the blade is circular and has a pin 62 fixed therein to extend perpendicular to the outer face thereof and in axial alignment with the projecting end of the ground blade. A pin 63 is fixed in the plug body 1' to extend parallel to pin 62 and in axial alignment with the blade 60. A spring '64 connects pins 62 and 63 to normally bias the blade 60 to a projecting position vertically from the end face of. the plug. A terminal screw 65 connects toa metal strap 66 connected to pin 61 and thereby to the plug body providing a ground terminal. The outer end of the ground blade 60 is conical at 67. If the plug is applied to a three-pole receptacle, the ground blade in its normal position will readily seat thereto with the circuit blades. But in the event that a two-pole utility outlet must be employed, the engagement of the conical end of the ground blade to the blank face of the receptacle provided as the circuit blades are directed to their appropriate sockets will cause the ground bladeto be cammed to an inoperative position against the bias of spring 64 permitting a power connecis provided on the base of the blade at a point spaced 90 from the notch42. A leaf spring 44 is provided with one end thereof fixed adjacent the blade 40 to the plug casing and its free end extending to normally engage in the notch 42 in the base of the ground blade.

In this manner the ground blade 40 is maintained in biased fashion in normally projected position as shown in Fig. 4 of the drawings. A terminal screw 45 afiords a connection to the ground blade it in its normally projected position the ground blade adapts the plug for use tion by the plug. As is readily obvious from the drawings, on removal of the plug from the receptacle, the

'ground blade will be biased to its normal projected position.

with a three-pole receptacle, affording a ground connection for the non-current carrying metal parts of the electrical equipment with which it is employed. In the event that only a conventional two-pole utility outlet is available to'power the electrical equipment, then the ground blade 40 is caused to be pivoted 90 to its inoperative position at which point the end of spring 44 engages in the notch 43 in the base of the blade as shown in Fig. 5 of the drawings. Thus, the plug adapts itself to the two pole outlet and it is avaiiable for immediate use as a three-wire grounding type electrical connector plug merely by'pivoting the blade -il back to its normally projected position at which point the spring 44 engages in As can be seen from the embodiments of the invention presented herein, a three-wire grounding type electrical connector plug of an improved nature is afforded by the invention which eliminates the need for adapters when only two-pole utility outlets are available to power portable electrical equipment. The irnproved plugalo insures that a power connection can be efiected irrespective of the nature of the outlet available without mutilation or disassembly thereof. And it provides, in its preferred form, a ground blade element which will automatically adapt itself to the outlet with which it is employed. In its simplicity the invention affords a plug which eliminates the necessity of having adapters on hand and the nuisance of disassembly thereof when the ground blade is not used. It affords an economical and efficient solution of the problem to which it is directed. i

From the above description it will .be readily apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable; but which obviously is susceptible of modifications in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages. a

While in order to comply with the statutes the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprises the preferred forms of several modes of putting the invention into eifect, and the invention is therefore claimed in any of its forms, or modifications, within the legitimate and 'valid scope of the appended claims.

Having thus described my invention, I claim:

1. An electrical connector plug comprising, a body of insulating material mounting circuit contact blades thereto at one face so as to project therefrom, a ground blade, pin means pivotally connecting said ground blade to said body adapting it to project therefrom in the manner of said contact blades, and spring means about said pin means operatively connecting to said ground blade and said body to normally maintain the projection of said ground blade and accommodate automatic bias of said ground blade relative said body on application of said plug to a receptacle which will not accommodate said ground blade therein, said ground blade having its extremity contoured to provide a cam surface with a high point displaced from the center line of the ground blade to insure said automatic bias.

2. An electrical connector plug comprising, a plug body of insulating material having circuit contact blade means mounted to project from one face thereof, ground blade means pivotally connected to said body at one face thereof, and spring means operatively connecting said ground blade and said body normally maintaining said ground blade in a projected position in the manner of said contact blades and automatically responsive to ap plication of said plug to a receptacle which will not accommodate said ground blade to provide for displacement of said ground blade from its normal projected position where it is held under the influence of said spring means, said spring means operatively connecting said ground blade and said body being so connected thereto that on removal of said plug from a receptacle not accommodating said ground blade said spring means will automatically return said ground blade to its normal projected position.

3. A three-wire grounding type electrical connector plug comprising, a body member apertured to receive a power cord therethrough, circuit contact blades seated in fixed relation to said body affording terminals for the circuit wires of the power cord, a ground blade normally projected from said body with said contact blades having a configuration distinct from said contact blades providing a sloping cam surface at its projecting extremity, and means connecting said ground blade to said body for automatic adjustment relative thereto upon application of said plug to a receptacle which will not accommodate said ground blade and automatic projection on removal from the receptacle.

4. An electrical connector plug comprising, a body member of insulating material having circuit contact blades mounted thereto in a recess in one end face thereof so as to project therefrom, a hinge bracket seated in said end face having a pivot pin transversely thereof, a ground blade mounted on said pin for rotation thereabout, a coil spring about said pin with its ends respectively biasing against said blade and said body to normally maintain said ground blade in a projected position in the manner of said contact blades, a camming slope on the projecting end of said ground blade, and a notch in the side of said body opening into said recess in the path of the ground blade whereby in absence of a proper Ieceptacle accommodating said ground blade, on application of said plug to a conventional outlet, said ground blade will be automatically cammed against the bias of said spring to lie parallelto said end face of said plug body and extend through said notch therein, and on removal of said plug, said ground blade will be biased to its normal projected position.

5. An electrical connector plug comprising, a plug body having circuit blades projecting from one face, a ground blade, means pivotally connecting said ground blade to said bodyat one side thereof adapting it to project in the manner of said circuit blades, a carnming contour provided on the outer end of said ground blade, and biasing means to said one side of said body normally engaging and maintaining said ground blade in its projecting position in the manner of said circuit blades, said camming contour being so formed on application of said plug to a receptacle which will not accommodate the ground blade, said ground blade will be automatically cammed from its normal position.

6. An electrical connector plug comprising, a plug body having circuit blades seated thereto so as to project from one face, a ground blade, means pivotally connecting the ground blade to said body at one side, spring means connected at its respective ends to said body and said ground blade so as to normally axially align with said ground blade and maintain a biased projection thereof in the manner of said circuit blades and maintain a rotative counter-bias on said ground blade on pivoting thereof, said ground blade having a sloping cam contour on its projecting extremity so formed and said spring means and said ground blade being so connected whereby on application of said plug to an outlet which will not accommodate said ground blade, said blade will be automatically cammed to an inoperative position providing for seating of said circuit blades to the outlet without interference from said ground blade and on release of the plug said ground blade will be automatically projected in the manner of said circuit blades by said spring means.

7. An electrical connector plug comprising, a plug body having circuit blades mounted thereto so as to project from one face, a pin seated in one side of said body, a ground blade unit pivotally mounted on said pin for movement generally continuously parallel to said one side of said body, said blade unit having notches in the inner connected portion thereof, and spring means connected to said plug body and operative to selectively engage in said notches on rotation of said ground blade unit parallel to said one side of said body to adapt said plug for application to a grounding type receptacle or a conventional two-pole utility outlet to make a power connection.

8. A three-wire, grounding type electrical connector plug comprising, a plug body of insulating material mounting circuit blades thereto in projecting relation therefrom, said body having a longitudinal recess in one side thereof, a pin mounted to said body within said recess and projecting therefrom, a ground blade pivotally mounted to said pin, biasing means connecting said pin and said ground blade to normally bias said ground blade into said recess on alignment therewith so as to cause it to project from said plug body in the manner of said circuit blades thus adapting said plug for application to a three-pole grounding type outlet, said ground blade being displaceable against the bias of said biasing means and pivotal on said pin to readily adapt said plug for application to a two-pole outlet.

9. An electric connector plug including a body element having circuit blades projecting from one face, a groove in the side of said body, a ground blade seated in said groove to project commonly With said circuit blades, pivot means connecting said pin to said body, said ground blade being slidable and pivotable on said pivot means outwardly of said body to clear said one face to enable application of the plug selectively to a two-pole outlet.

170; An electrical connector plug comprising, a plug body having a pair of circuit blades projectingfrorn one face, a notch in one side of said plug body; a ground blade; a pivot pin pit/ otally mounting said ground blade to said plug body, a'spring about said pivot pin maintaining a constant bias on. said ground blade and efiective to maintain said ground blade in a normal projected position parallel to said circuit blades, said ground blade being adapted thereby to-be selectively biased into said References Cited in the file of this patent notch with said spring maintaining its continuous bias in thereon in the process.

UNITED STATES PATENTS Dorsey 1 11.14, 1919 Tousley July 6 1943 FOREIGN PATENTS i Great Britain Apr. 6, 1933 France Q. Dec,'12, 1935 

